Air-cooled oil sump with fins for receiving oil in a heat exchange relationship

ABSTRACT

A sump for internal combustion engines, having external fins for flow of cooling air thereover, the sump receiving hot oil returned from the engine and having internal passages in heat exchange relationship with the finned surface, the returned oil being pressurized within the sump and forced through the internal passages for efficient cooling before being again circulated through the engine. The sump is usable without modification on engines with the axis either vertical or horizontal or at any angle therebetween.

United States Patent Jones AIR-COOLED OIL SUMP WITH FINS FOR RECEIVING OIL IN A HEAT EXCHANGE RELATIONSHIP Charles Jones, Hillsdale, NJ,

Curtiss-Wright Corporation, Wood-Ridge, NJ.

Filed: Mar. 14, 1974 Appl. No.: 451,055

lnve ntor:

Assignee:

US. Cl. l84/l04 B; 165/164 Int. Cl. Fl6n 13/00; FOlm 5/00 Field of Search 184/104 B; 165/169, 164,

References Cited UNITED STATES PATENTS Weschler ct a1. 165/80 Kremser 184/104 B X June 24, 1975 2,829,290 4/1958 VanWarmerdam 165/74 Primary Examiner-Richard C. Pinkham Assistant Examiner-William R. Browne Attorney, Agent, or Firm-Raymond P. Wallace;

Victor D. Behn [57] ABSTRACT A sump for internal combustion engines, having external tins for flow of cooling air thereover, the sump receiving hot oil returned from the engine and having internal passages in heat exchange relationship with the finned surface, the returned oil being pressurized within the sump and forced through the internal passages for efficient cooling before being again circulated through the engine. The sump is usable without modification on engines with the axis either vertical or horizontal or atany angle therebetween.

11 Claims, 10 Drawing Figures PATENTEDJUM 24 I975 SHEET III)! PATENTEI] JUN 24 m5 SHEET FIG. 2

PATENTEDJUN24 ms 11% 8 91, 059 sum 4 FIG/0 AIR-COOLED OIL SUMP WITH FINS FOR RECEIVING OIL IN A HEAT EXCHANGE RELATIONSHIP BACKGROUND This invention relates to oil sumps for internal combustion engines. and more particularly to such sumps wherein hot oil from the engine is cooled by air flow over a finned structure before being recirculated through the engine.

In the prior art, oil sumps for internal combustion engines have generally been located sufficiently remotely from the region of heat input, and have been of sufficient capacity, that no special cooling measures were necessary. In other cases the sump has had a cooling medium flowing over its exterior surface, but such an arrangement had a relatively minor effect, since the mass of oil did not cool rapidly, and the intake of the oil pumping means did not necessarily receive the coolest oil from the reservoir. Such sumps were generally formed of sheet metal and were, in effect, merely pans or tanks which did not lend themselves to any complexity of configuration or sophistication of design for cooling, owing to the difficulty and expense of assembly.

Although such expedients have sometimes been satisfactory in the prior art, particularly with large engines of fixed orientation and wherein the oil had only a lubricating function, they are not suitable for small engines which cannot accommodate a sump of large capacity, nor for engines which must be of light weight and which may have changes of orientation during use, and wherein the oil has an engine cooling function as well as lubricating. This invention overcomes those limitations of the prior art.

SUMMARY This invention provides an inexpensive and readily assembled die-cast oil sump for internal combustion engines, which isusable or engines having either a vertical or a horizontal axis, or which are tiltable to angles therebetween, as in handheld or mobile power tools. Hot oil from the engine is received within the sump and is then circulated under pressure and at high velocity through a cooling system before being returned to the engine. The sump is provided with external fins cast integrally with the sump body, with cooling air flowing thereover, and contains an internal pump which intakes oil from the sump reservoir chamber and pumps it at high velocity through passages of small cross-section in close juxtaposition to the finned area and in heat exchange relationship therewith, and thence to the engine for cooling and lubrication before it is returned to the sump.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an external view of an internal combustion engine with the oil sump disposed at one end thereof;

FIG. 2 is a plan view, partly in cross-section, of the oil sump of the invention;

FIG. 3 is a cross-sectional elevation taken on line 33 of FIG. 2;

FIG. 4 is a fragmentary view taken on line 4-4 of FIG. 3, showing one orientation of the oil passages within the sump;

FIG. 5 is a view similar to FIG. 4 showing another orientation of the oil passages;

FIG. 6 is an exploded perspective view showing an alternate mode of forming the passages of FIG. 4;

FIG. 7 is a cross-section showing still another mode of forming the passages;

FIG. 8 is a view showing the external fins and the internal oil passages die-cast in a single element;

FIG. 9 is a cross-sectionalelevation of the sump showing a different orientation of the internal oil passages; and

FIG. 10 is a similar view showing a different orientation of the cooling fins.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. I shows generally an internal combustion engine ll suitable for lawnmowers, powered portable tools, and the like. The engine may be either a rotary engine or of the reciprocating piston type, and although shown in vertical orientation it may also be used horizontally. At the bottom, as shown, of the engine is disposed an oil sump 12 to be described below. The top portion of the engine is provided with an enclosed fan 13 for circulating cooling air past the fins of the sump in the direction shown by the arrows. A jacket 14 confines the air to the desired path. It will be understood that the fan may be otherwise positioned, such as below the sump, and that any suitable ducting arrangement may be employed to direct the air. As shown the air flows in the longitudinal direction over cooling fins projecting generally radially from the sump, but an embodiment will be hereinafter described in which the sump has circumferential fins and the cooling air is directed around them through an appropriate volute.

FIGS. 2 and 3 show the construction of the die-cast sump 12. The sump comprises a generally annular body member 16 having double concentric walls 17 and 18 spaced apart radially by fins 19 having longitudinal extent in the axial direction for flow of cooling air thereover, as shown by arrows in F IG. 3. The fins are integral with at least the inner wall 18 of the body member, and may, as shown, be also integral with the outer wall 17, uniting the two walls 17 and 18 into a single unit 16. In some cases it may be preferred to have the fins integral with only the inner wall 18 and to form the outer wall I7 by sheet metal subsequently applied. The fins 19 may be disposed radially between the two walls; such an arrangement will result either in the fins being of constant thickness with the air passages therebetween of somewhat wedge-shaped cross-section, or in wedgeshaped fins with passages of constant cross-section, or with the discrepancy being distributed between the fins and the passages so that both are of slightly greater cross-section at the periphery. As shown in FIG. 2 both the fins and the passages are of constant cross-section and disposed in generally radial groups around the circumference, with wedge-shaped passages separating adjacent groups.

In a liquid-to-gas heat exchange relationship such as the sump of this invention, it is necessary for the most efficient operation that the fins be as thin as possible and closely spaced. and have a radial dimension several times as great as the spacing between fins. For this reason, the thickness of the fins and the spacing therebetween are approximately equal, and the radial dimension ofthe fins is from about six times to about 12 times the fin thickness. For better heat exchange. the fins are also filleted into the walls 17 and 18 at their junctions therewith.

In the embodiment shown in FIG. 3 the bottom of the sump is closed by a wall 21 which is die-cast integral with the inner peripheral wall 18. The top is closed by a closure member 22, which in a permanent assembly may be soldered or bolted in place, but as shown in FIG. 3 is a removable cover which is retained by the mounting of the sump against the engine housing, the closure 22 resting against a gasket 23 to seal against leakage of oil. The drive shaft 24 of the engine transpierces the cover 22, and may also transpierce the bottom wall 21 when it is contemplated that the power take-off will be at the bottom end, as shown in FIG. 1. In cases where the power take-offis at the top, the shaft may merely extend into the sump for driving the oil pump. In some cases it may be desirable to position the closure 22 at the bottom.

An oil pump 26 is positioned within the sump, in driven engagement with shaft 24. The pump may also be indirectly driven from the shaft, or may be driven by electrical means. The oil pump may be of any suitable type, such as the gear pump shown, having oil intake means 27 positioned adjacent to the bottom of the sump and adjacent to the periphery thereof. The oil level within the sump will normally be well above the intake 27 so that the intake is always immersed when the engine is used in the vertical position. The intake is positioned adjacent to the periphery of the pump chamber 28 in the zone which will comprise the bottom of the sump when the engine is used horizontally, that is, if the showing of FIG. 3 were rotated 90 in the clockwise direction, and hence the intake will still always be below the oil level.

An annular die-cast insert 29 is disposed inside circumferential wall 18 and defines the diameter of the pump chamber 28. The annular insert 29 is provided on its outer circumference with a plurality of ribs 31 extending in the axial direction, parallel with the shaft 24. Ribs 31 are of slightly shorter length than the annular wall of insert 29, being alternately flush with the top and bottom ends of the insert and short at the opposite ends, the difference in length between the ribs and the wall being approximately equal to the spacing between ribs. The circumferentially outer faces of ribs 31 fit tightly against the inner circumference of finned wall 18, so that in the assembled state they define a continuous replicate passage 32 between insert 29 and wall 18, with the passes of passage 32 leading alternately from bottom to top and around substantially the entire periphery of the pump chamber. A single rib 33 (shown in FIG. 4) has the same axial dimension as the annular wall of insert 29, its end thus being in contact with the bottom 21 of the sump and the cover 22, to prevent the passage 32 from rejoining itself.

The oil output from pump 26 is discharged through any suitable passage means, which may be a tube 34 as shown in FIG. 3, connected into one end of passage 32 adjacent to rib 33. A further passage means, which may be a tube 36, receives the oil at the end of the passage 32 and conveys it to the engine for its cooling and lubricating functions. Hot oil returns from the engine to the sump through any suitable passage means. such as tube 37.

It will be seen that hot oil from the sump is circulated under pump pressure around the cooled periphery of the sump, at a high scrubbing velocity through a replicute passage having a plurality of passes of alternating direction generally parallel to the shaft axis. The passes between ribs 3l are defined on their inner circumferential sides by the annular wall of insert 29 and on their outer circumferential sides by the thin, finned wall 18 having cooling air flowing over the fins. Each element of the sump is pressure die-cast, or cast in other types of permanent mold. At least the body member [6 should be cast from a metal of high thermal conductivity, such as alloys of aluminum, magnesium, or zinc. The insert 29 need not have high thermal conductivity, but it is usually convenient to form it of the same alloy as the body member.

Although pressure die-casting in a ram-fed permanent mold is the preferred method of forming the sump members, die-casting in other types of permanent mold is satisfactory. such as centrifugal casting, or casting in a gravity-fed permanent mold wherein the necessary pressure is obtained from a head of molten metal in a reservoir.

Although the elements ofthe sump can be formed by sand casting, the design of the sump of this invention is such that it can be cast without coring, the cavities in the cast article all being such that they can be formed by slides or fingers in the mold which can be pulled from one direction, which renders it peculiarly suitable for permanent mold casting. It is also possible for the sump structure to be built up from individual elements brazed, soldered, or welded together, although in the present state of the art such a procedure would be considerably more expensive than permanent mold casting.

The transverse cross-section of the replicate passage 32 is substantially constant throughout, such crosssection being of lesser area than the transverse crosssection of an air passage between any two fins 19. The passage 32 has a radial dimension no greater than its circumferential dimension, the radial dimension of passage 32 also being considerably less than the radial dimension of passage 32 also being considerably less than the radial dimension of the air passages between fins 19. Thus it is assured that there is a sufficient mass of air flowing over the fins for efficient extraction of heat from the oil, and that no portion of the oil traversing passage 32 shall be radially remote from cooled wall 18.

In some engines wherein the heat load to be dissipated is not too great, it may be unnecessary to have the hot oil traverse the entire periphery of the sump, and the separating rib 33 may be omitted so that the passage 32 rejoins itself and is continuous all the way around. In such a case the pump feeds oil into the passage at any selected point and the oil travels through the passage in both directions therefrom, the two flows meeting at about I around the circumference from the entrance point and being discharged through passage means 36 which is then disposed at the meeting point of the two flows.

It is not always necessary that the replicate passage have its passes parallel and oriented in the precisely axial direction as shown in FIG. 4. FIG. 5 shows an embodiment wherein the replicate passage 32a has its passes disposed in the generally axial direction but somewhat angled therefrom, the separating ribs 310 being in the shape of acute triangles with their apexes alternately oriented. This results in a somewhat faster oil flow through the passage, although the passage 32a has less total length than passage 32 of the previous embodiment.

FIG. 6 shows an alternate method of forming the two principal elements of the sump. Instead of all the ribs 3I being integral with the wall of insert29 as in the embodiment of FIGS. 2-5, alternate ribs are formed integral with the wall of 29 and the remainder are integral with the inner finned wall I8. In this case the ribs may be shortened at the top end of either member and at the bottom end of the other, in order to form the continuous replicate passage 32 when the two parts are assembled.

FIGS. 7 and 8 show still further modes of forming the passage. In FIG. 7 all the ribs 3i are formed in the outer member, integral with the finned wall 18, and the insert 29 is a simple smooth cylindrical member fitting tightly against the inner circumference of the array of ribs. In FIG. 8 the sump structure is cast as a single piece, with wall 29a being not an insert but integral with the ribs 3i, which in turn are integral with the finned wall 18. This mode is a more difficult casting problem, but may be employed when it is desired that there should be absolutely no leakage transversely across ribs 31. In the other embodiments there may be a very slight amount of such leakage, but since the parts are very closely fitted it is of little significance. The modes of FIGS. 6, '7, and 8 may also be used to form the replicate passage 32a of FIG. 5.

In FIG. 9 there is shown an embodiment in which the replicate passage means 32h extends in the circumferential direction rather than axial. Passage 32b has approximately the same cross-section as in the other embodiments, but is helical around the circumference of insert 29b. In other respects the sump is formed in the same manner as the embodiment of FIG. 3, except that in FIG. 9 closure 22 is shown positioned at the bottom. This arrangement is not necessitated by the nature of the replicate passage, but is shown to illustrate that the closure may be either at top or bottom of the several embodiments, as may be convenient.

FIG. 10 shows an embodiment in which the aircooled fins 19 cast integrally with wall 18 have the same general radial, thickness, and spacing proportions as those previously described, but their longitude is circumferential rather than axial. In this embodiment the outer circumferential wall 17 is not integral with the fins and may be either a die-cast cylindrical member or sheet metal retained by any suitable means, defining a volute surrounding the fins to confine the air to a circumferential path. Cooling air is introduced into the volute and taken off through suitable apertures (not shown). A closure member 22 is disposed at both the top and bottom of the oil sump 12, as an illustration of the flexibility of the design. Although the insert 291) shown is that of FIG. 9, any of the forms of insert 29 previously described may be used in this embodiment.

Although the embodiments of the sump I2 are all shown in the drawings as of circular cylindrical form, the sump may also be elliptical, oval, or of other convenient shape desired in a particular application, and the term "generally annular" used herein is intended to inelude such shapes. Mounting means such as flanges, lugs. or the like are conventional and are not shown, as not being necessary to an understanding of the invention. as is also the case with such elements as shaft seals. bearings, and the like.

What is claimed is:

l. A coolable oil sump for use with an internal combustion engine, comprising a generally annular body member having external fins extending radially from the periphery thereof for flow of cooling air thereover, a generally annular insert disposed within the body member, the insert having a hollow interior defining a pump chamber receiving hot oil from the said engine and its exterior periphery defining with the inner periphery of the body member elongated replicate oil passage means in communication with the pump and disposed between the body member and the insert, the replicate oil passage means being in contact with the inner periphery of the cooled body member in heat exchange relationship therewith, an oil pump disposed within the pump chamber and having means for taking in oil, the pump discharging hot oil into the said replicate oil passage means for cooling, and output passage means receiving the cooled oil from the replicate oil passage means and delivering the cooled oil to the said engine for recirculation therethrough.

2. The combination recited in claim I, wherein the thickness of the external tins and the spacing therebetween are approximately equal, and the radial extent of the fins is a plurality of times greater than the spacing therebetween.

3. The combination recited in claim 2, wherein the pump chamber has an axis, the generally annular wall of the insert being coaxial therewith, the pump chamber having a second wall generally normal to the axis and meeting the generally annular wall at an angle thereto, and the intake means for the oil pump is disposed in the meeting angle adjacent to the generally annular wall in a region having a lowermost position of the pump chamber when the axis is disposed horizontally, and also adjacent to the second wall in a region having a lowermost position of the pump chamber when the axis is disposed vertically.

4. The combination recited in claim 3, wherein the sump has an axis coaxial with the generally annular insert, and the replicate passage means comprises a plurality of interconnected passes generally parallel to the axis.

5. The combination recited in claim 4, wherein the interconnected passes of the replicate oil passage means are spaced around approximately the entire periphery of the pump chamber insert, the pump discharge being receivcd at one end of the replicate passage means and being discharged therefrom at the other end thereof after flowing around approximately the entire periphery of the pump chamber.

6. The combination recited in claim 4, wherein the interconnected passes of the replicate oil passage means are spaced around the entire periphery of the pump chamber insert, the pump discharge being received in the replicate oil passage means at a come nient location and flowing therethrough in both directions around the periphery, and being discharged therefrom at a location approximately opposite its point of entry.

7. The combination recited in claim 4, wherein the plurality of interconnected passes of the replicate passage means are generally parallel to the axis but slightly angled alternately therefrom in a zigzag path.

8. The combination recited in claim 3, wherein the sump has an axis surrounded by the generally annular insert, and the replicate passage means comprises a helix surrounding the axis.

body member in a generally circumferential direction. and the fins have an external sheath comprising a volute for directing cooling air around the fins.

ll. The combination recited in claim 3, where the pump is driven by the shaft of the internal combustion engine. 

1. A coolable oil sump for use with an internal combustion engine, comprising a generally annular body member having external fins extending radially from the periphery thereof for flow of cooling air thereover, a generally annular insert disposed within the body member, the insert having a hollow interior defining a pump chamber receiving hot oil from the said engine and its exterior periphery defining with the inner periphery of the body member elongated replicate oil passage means in communication with the pump and disposed between the body member and the insert, the replicate oil passage means being in contact with the inner periphery of the cooled body member in heat exchange relationship therewith, an oil pump disposed within the pump chamber and having means for taking in oil, the pump discharging hot oil into the said replicate oil passage means for cooling, and output passage means receiving the cooled oil from the replicate oil passage means and delivering the cooled oil to the said engine for recirculation therethrough.
 2. The combination recited in claim 1, wherein the thickness of the external fins and the spacing therebetween are approximately equal, and the radial extent of the fins is a plurality of times greater than the spacing therebetween.
 3. The combination recited in claim 2, wherein the pump chamber has an axis, the generally annular wall of the insert being coaxial therewith, the pump chamber having a second wall generally normal to the axis and meeting the generally annular wall at an angle thereto, and the intake means for the oil pump is disposed in the meeting angle adjacent to the generally annular wall in a region having a lowermost position of the pump chamber when the axis is disposed horizontally, and also adjacent to the second wall in a region having a lowermost position of the pump chamber when the axis is disposed vertically.
 4. The combination recited in claim 3, wherein the sump has an axis coaxial with the generally annular insert, and the replicate passage means comprises a plurality of interconnected passes generally parallel to the axis.
 5. The combination recited in claim 4, wherein the interconnected passes of the replicate oil passage means are spaced around approximately the entire periphery of the pump chamber insert, the pump discharge being received at one end of the replicate passage means and being discharged therefrom at the other end thereof after flowing around approximately the entire periphery of the pump chamber.
 6. The combination recited in claim 4, wherein the interconnected passes of the replicate oil passage means are spaced around the entire periphery of the pump chamber insert, the pump discharge being received in the replicate oil passage means at a convenient location and flowing therethrough in both directions around the periphery, and being discharged therefrom at a location approximately opposite its point of entry.
 7. The combination recited in claim 4, wherein the plurality of interconnected passes of the replicate passage means are generally parallel to the axis but slightly angled alternately therefrom in a zigzag path.
 8. The combination recited in claim 3, wherein the sump has an axis surrounded by the generally annular insert, and the replicate passage means comprises a helix surrounding the axis.
 9. The combination recited in claim 3, wherein the sump has an axis surrounded by the generally annular body member, and the fins for air cooling extend in a direction generally parallel to the axis.
 10. The combination recited in claim 3, wherein the sump has an axis surrounded by the generally annular body member, the fins for air cooling surround the body member in a generally circumferential direction, and the fins have an external sheath comprising a volute for directing cooling air around the fins.
 11. The combination recited in claim 3, where the pump is driven by the shaft of the internal combustion engine. 